Emergency — phone the vet nowImmediately — heat stroke is fatal if not treated within minutes to hours. Sepsis requires emergency IV treatment. Both are life-threatening emergencies.

Dog with bright red gums

Bright red gums with panting, vomiting, or collapse could be heat stroke or sepsis — call your vet or emergency vet immediately and begin cooling if heat stroke is suspected.

Dog

In the next 60 seconds

1. CALL YOUR VET IMMEDIATELY — describe the gum colour and accompanying signs.
2. If heat stroke is suspected: Move the dog immediately to a cool, shaded, or air-conditioned area.
3. Begin cooling with cool (not ice cold) water — pour or sponge over the neck, armpits, and groin areas where blood vessels are close to the surface. Do NOT use ice or ice-cold water — this causes peripheral vasoconstriction and traps heat in the core.
4. Use a fan to increase evaporative cooling while applying cool water.
5. Offer cool water to drink only if the dog is conscious and able to swallow — do not force it.
6. Measure temperature if you have a thermometer — inform the vet. Stop active cooling once the dog's temperature reaches 39.5°C to avoid over-cooling.
7. Drive to the vet immediately — do not wait for the temperature to normalise at home. Internal damage from heat stroke continues even after external temperature drops.
8. If carbon monoxide is suspected: get all animals and people out of the building immediately, call 999, and get into fresh air.
9. If sepsis is suspected based on signs of infection: go to the emergency vet without delay — sepsis progresses rapidly.

Recognise the signs

Gum colour: bright red, brick red, or 'fire engine' red — versus normal salmon-pink
Capillary refill time may be very fast (under 1 second) in early vasodilatory states
Heat stroke signs: excessive panting, hypersalivation (thick ropy saliva), vomiting, bloody diarrhoea, stumbling and staggering, glazed eyes, high body temperature (above 41°C is dangerous), eventual collapse and seizures
Sepsis signs: fever or low temperature, rapid breathing, altered mentation, recent signs of infection (wound, UTI, pyometra, dental abscess)
Carbon monoxide: multiple animals or people in the household affected simultaneously, history of faulty boiler or enclosed space
Progressive deterioration without intervention in all causes

First aid steps

1. CALL YOUR VET IMMEDIATELY — describe the gum colour and accompanying signs.
2. If heat stroke is suspected: Move the dog immediately to a cool, shaded, or air-conditioned area.
3. Begin cooling with cool (not ice cold) water — pour or sponge over the neck, armpits, and groin areas where blood vessels are close to the surface. Do NOT use ice or ice-cold water — this causes peripheral vasoconstriction and traps heat in the core.
4. Use a fan to increase evaporative cooling while applying cool water.
5. Offer cool water to drink only if the dog is conscious and able to swallow — do not force it.
6. Measure temperature if you have a thermometer — inform the vet. Stop active cooling once the dog's temperature reaches 39.5°C to avoid over-cooling.
7. Drive to the vet immediately — do not wait for the temperature to normalise at home. Internal damage from heat stroke continues even after external temperature drops.
8. If carbon monoxide is suspected: get all animals and people out of the building immediately, call 999, and get into fresh air.
9. If sepsis is suspected based on signs of infection: go to the emergency vet without delay — sepsis progresses rapidly.

Do NOT

Do NOT use ice or ice-cold water on a heat stroke dog — this causes peripheral vasoconstriction and can worsen the condition.
Do NOT submerge the dog in cold water.
Do NOT leave the dog in the car to cool down on its own — it will continue overheating.
Do NOT muzzle the dog — they need to pant to release heat.
Do NOT over-cool — stop active cooling once temperature reaches 39.5°C.
Do NOT wait to see if the dog improves on its own when gums are bright red with other signs.
Do NOT confuse very dark pigmented gums with bright red gums — check the inner eyelid (conjunctiva) which is less pigmented.

While transporting to the vet

For heat stroke: continue cooling with wet towels over the body during transport. Keep the car air conditioning on maximum.
Do not wrap the dog in dry towels or blankets — this traps heat.
Keep windows open.
Phone the vet to notify them you are coming so they prepare IV fluids and cooling equipment.
Monitor breathing and gum colour throughout the journey.

When to phone the vet immediately

Bright red gums with any degree of collapse, staggering, or loss of consciousness
Bloody diarrhoea or vomiting alongside bright red gums (severe heat stroke sign)
Seizures
Temperature above 41°C
Multiple animals in the household affected (carbon monoxide)
Signs of infection preceding the red gums (abscess, wound, pyometra)
Gum colour changing from bright red to pale or blue (cardiovascular collapse)

When it can usually wait

There are no circumstances where bright red gums with systemic signs should wait.
A dog with very dark pink (but not bright red) gums after mild exercise in warm weather who is otherwise normal and cools down within 5 minutes — monitor closely but may not be an emergency.

Common causes

Heat stroke (hyperthermia) — most common cause in UK summer; also from being left in cars, over-exercise in heat, brachycephalic breeds
Sepsis/systemic inflammatory response syndrome (SIRS) — overwhelming bacterial infection causing vasodilation
Early/hyperdynamic shock — vasodilation phase before cardiovascular collapse
Carbon monoxide poisoning — cherry-red colouration of haemoglobin
Certain toxins causing vasodilation
Polycythaemia — too many red blood cells making gums appear very dark red or brick red
Normal variation in some pigmented-gum breeds (misleading — compare to inner eyelid)

What the vet will need to know

Environmental temperature and what the dog was doing before symptoms
Has the dog been in a car, conservatory, or enclosed hot space?
Duration of symptoms and any progression
Current body temperature if measured
Any recent signs of infection — wound, discharge, urinary symptoms?
Any toxin or medication exposure?
Other animals or people in the household affected?
Dog's breed, age, weight, and any known health conditions
Is the dog able to drink, stand, and walk?

Aftercare

Heat stroke causes internal organ damage — kidneys, liver, clotting system, brain — that may not be immediately apparent. Monitoring in hospital with IV fluids is essential.
Dogs that survive severe heat stroke require serial blood tests over 24–72 hours to assess organ function.
Disseminated intravascular coagulation (DIC) is a life-threatening complication of severe heat stroke.
After discharge: strict rest in a cool environment, restricted exercise, monitoring for delayed signs of organ damage.
Dogs with a history of heat stroke are at higher risk of recurrence — discuss exercise and environmental management with your vet.
Avoid exercise in warm weather permanently or apply strict heat management strategies.

Prevention

Never leave dogs in cars — even on cool cloudy days. A car can reach 47°C within 30 minutes on a 22°C day.
Walk dogs early morning and late evening in warm weather.
Ensure constant access to fresh water and shade.
Never force exercise in heat — even fit, healthy dogs can overheat.
Brachycephalic breeds should not be exercised in temperatures above 18–20°C.
Install carbon monoxide detectors in the home.
Treat infections promptly to prevent progression to sepsis.

Breed-specific notes

French Bulldogs, Pugs, Bulldogs, Shih Tzu, Pekingese, Boston Terriers: brachycephalic breeds are at extreme risk of heat stroke — their obstructed airways mean they cannot pant effectively to cool down. Keep them indoors in air conditioning above 20°C.
Chow Chows and St Bernards: thick double coats, prone to overheating.
Overweight dogs of all breeds: reduced efficiency of heat dissipation.
Working dogs (Border Collies, Spaniels): may continue working past the point of overheating due to drive.

Frequently asked questions

How hot does it have to be for my dog to get heat stroke in the UK?

Heat stroke can occur in UK conditions — dogs have died from heat stroke at outside temperatures of just 20°C when confined in direct sun or a parked car. Humidity matters too — high humidity prevents effective evaporative cooling from panting. Brachycephalic breeds can overheat at even lower temperatures. The key risks are: enclosed spaces (cars, conservatories), direct sun with no shade, high humidity, and exercise in warm weather.

I've seen videos suggesting putting wet towels over a heat-stroke dog — is this safe?

Wet towels applied to the dog's body can help cooling, but there is an important nuance: do not cover the dog with towels and leave them — this traps heat against the body. Instead, keep the towels actively wet, fan the dog, and frequently refresh the water. The most effective areas to target are the neck, armpits, and groin. The goal is to evaporate the water off the dog's body, which is why airflow (fanning) is also essential.

My dog has bright red gums but seems fine — do I still need to go to the vet?

Yes — at minimum, call your vet and describe the colour and all accompanying signs in detail. Very bright red gums that persist without obvious cause (mild post-exercise flush that resolves quickly) always warrant assessment. Some conditions, particularly early heat stroke and early sepsis, can initially present with a 'false normal' where the dog seems okay but is compensating — this can deteriorate rapidly.

What is sepsis and how would my dog get it?

Sepsis is a life-threatening organ dysfunction caused by a dysregulated response to infection. In dogs, common sources include pyometra (infected uterus — particularly in unspayed middle-aged or older bitches), infected wounds, dental abscesses, urinary tract infections that spread to the kidneys, and post-surgical infections. A dog with sepsis needs emergency IV antibiotics and fluid support. Signs include fever or hypothermia, rapid breathing, weakness, and altered mentation.

Can I give water to a dog with heat stroke?

Yes, offer cool water to drink — but only if the dog is conscious, alert, and can swallow safely. Do not pour water into the mouth of a dog that is confused, staggering, or has reduced swallowing reflex — this risks aspiration into the lungs. Do not give very cold or iced water — cool or room temperature water is appropriate.